Halberstam became one of the youngest rebbes in Europe, leading thousands of followers in the town of Klausenburg, Romania, before World War II. His wife, eleven children and most of his followers were murdered by the Nazis while he was incarcerated in several concentration camps. After the war, he moved to the United States and later to Israel, rebuilt Jewish communal life in the displaced persons camps of Western Europe, re-established his dynasty in the United States and Israel, founded a Haredi neighborhood in Israel and a Sanz community in the United States, established a hospital in Israel run according to Jewish law, and rebuilt his own family with a second marriage and the birth of seven more children.

Halberstam was born in 1905 in the town of Rudnik, Poland. He was a great-grandson (through the direct male line) of Rabbi Chaim Halberstam of Sanz (the Divrei Chaim), one of the great Hasidic leaders of Polish Jewry, and a grandson of the Gorlitzer Rebbe, Rabbi Baruch Halberstam (1829–1906).[2] His father, Rabbi Tzvi Hirsch Halberstam, the Rav of Rudnik, instilled in the young Yekusiel Yehudah a love of Hasidut and Torah scholarship, sharing with him stories of how the Divrei Chaim learned, prayed and conducted his tish (Shabbat and Jewish holiday celebratory table).

When Yekusiel Yehudah was 13, his father died. Afterwards he studied with other leading Hasidic rebbes, including Rabbi Myer Yechiel of Ostrovtza, Rabbi Chaim ElazarSpira (the Munkatcher Rebbe), and his great-uncle, Rabbi Shalom Eliezer Halberstam of Ratzfert. During this period, Yekusiel Yehudah became known as the "ilui ("genius") of Rudnik,". In later years he would periodically return to Rudnik to visit with his followers, who remained loyal to him even after the appointment of his first cousin Rabbi Benyumin Teitelbaum-Halberstam as Rabbi in 1924.

In 1921, Halberstam married his second cousin, Chana Teitelbaum, the daughter of Rabbi Chaim Tzvi Teitelbaum, the Rabbi of Sighet, Romania. She was also a descendant of the Divrei Chaim: her maternal grandfather, Rabbi Sholom Eliezer Halberstam, was the sixth of the seven sons of the Sanzer Rav and his paternal grandmother was a sister of her paternal grandfather. The young couple lived in her father's house for the next five years.

In 1927, at the age of 22 and at the behest of his remote uncle Joel Teitelbaum, Halberstam accepted the post of Rabbi of the "Sefardi congregation" in Klausenburg, Romania. The group, comprising mainly hasidim, split from the official Orthodox community because of the alleged Zionism of Rabbi Moshe Glassner. They used a clause which allowed them to maintain an independent ("Status Quo") congregation. Although he was relatively young, he impressed the community with his charismatic personality, wisdom, and warmth toward Jews of all backgrounds. During the 16 years he spent there, he exhibited many of the qualities that would set him apart during his imprisonment by the Nazis. He slept only three hours a night, often on a synagogue bench, and he often ate only one meal a day, reserving bread for the Sabbath. He spent much of his day in prayer and study. His love for and faith in God was legendary. He also paid special attention to children, founding a yeshivah in which 100 students learned in Klausenberg.

The Rebbe's reputation spread throughout Romania and Hungary, and even reached Israel. In 1937 Halberstam was offered a seat on the Jerusalemrabbinical court. Uncertain as to whether he should accept the seat or stay with his community, Halberstam wrote to his mother in Rudnik for advice. She advised him to stay where he was, saying he was too young to accept such a position.

When World War II broke out, the Jews of Hungary and Romania were not immediately affected by the German offensive against Polish and Lithuanian Jewry. However, local anti-Semitism flourished. Following the Second Vienna Award of September 1940, Transylvania, previously given to Romania in the post World War I Trianon Treaty, was partitioned between Hungary and Romania. Northern Transylvania, including Kolosvar (in Hungarian; Cluj in Romanian and Klausenberg in German and Yiddish) was now part of Hungary, Germany's new Axis ally, rather than part of Romania. The strongly Hasidic and Orthodox Jewish communities of Transylvania such as Klausenberg and Satmar were now under the authority of the government in Budapest.

In 1941, a new law required all Jews living in Hungary to prove that their family had lived in and paid taxes in Hungary back to 1851. Suddenly thousands of Jews, including the Rebbe (who was born in Poland), were placed in jeopardy. The Rebbe, his wife and eleven children were arrested and brought to Budapest, where the family was separated. The Rebbe was jailed with a group of leaders who were eventually sent directly to Auschwitz. Thanks to the efforts of friends and supporters, the Rebbe was released and the family returned to Klausenberg.

Despite the danger, the Rebbe refused to leave his followers and made no effort to save himself from further searches. Instead, he threw himself into helping refugees from Nazi-occupied lands and tending to his followers. Between 1941 and 1944, the Rebbe never stopped studying Torah and praying for the Jewish people.

On March 19, 1944 the Germans invaded Hungary and Gestapo chief Adolf Eichmann immediately organized the round-up, ghettoization, and deportation of Hungarian Jews to Auschwitz. The Klausenberg ghetto was established on May 1, 1944, and was liquidated via six transports to Auschwitz between late May and early June. Knowing that the Gestapo targeted community leaders first, the Rebbe hid in an open grave in a cemetery for several weeks. He then fled to the town of Banya, where he was conscripted into a forced-labor camp along with 5000 other Hungarian Jews. Though hunger was not a problem here—the barbed-wire enclosure had a back exit through which Jews could buy bread and milk from non-Jews—the Hungarian soldiers constantly badgered and searched inmates for their valuables. The Rebbe shaved his beard as authorized by the Hungarian Chief Orthodox Rabbinate. He continued to conduct prayer services and even a Shabbat tisch. Conditions were not harsh, and he and many prisoners bribed the authorities to refrain from labor.

About a month after the Rebbe's arrival, the Arrow Cross took over Hungary. The inmates underwent selection, and while many who could work remained, the rest were loaded into cattle cars and dispatched to the Auschwitz death camp. Several months beforehand, the Rebbe's wife and nine of their children who remained with her were sent to Auschwitz on a transport from Klausenberg. They were gassed to death on June 2, 1944. Halberstam, however, survived the selection by Dr. Josef Mengele and was sent to work.

He attempted to remain fully observant in the inhuman conditions and to encourage his fellow prisoners. He never touched non-kosher food and refused to eat food cooked in a non-kosher pot. Often he went hungry. His staunch faith gave spiritual strength to many. He assured his fellow inmates that God was with them in the valley of death, and would not abandon them.

In late 1944, a year and half after the Warsaw Ghetto uprising, Halberstam was assigned to a special labor detail to clear out the ruined ghetto. He and 6000 other prisoners searched for valuables and demolished the ruins by hand and with rudimentary tools so that the Nazis could sell the bricks and steel to Polish contractors. As they beheld skeletons piled in the street, and uncovered bunkers in which Jews had died by gas or shooting, the Hungarian prisoners realized for the first time the extent of the annihilation of European Jewry.

This time the Rebbe did not shave his beard, which is considered a mark of holiness for Hasidim. He wrapped his beard and face in a handkerchief, pretending he had a toothache. This charade was accompanied by the fact that he cried all day as he worked, praying and communing with God.

When the prisoners began to hear rumors that their labor detail was about to be liquidated, they decided to try to escape rather than let the Nazis kill them. However, the Rebbe encouraged them to adopt a "wait and see" attitude. In response to one plan, in which prisoners would storm the camp gates and make a run for the forest, where they would connect with partisans, the Rebbe advised, "Until we see that the Nazis are about to exterminate us, it is prohibited for anyone to sacrifice his life and put himself in a situation of certain death. But one must remain vigilant, and as soon as it becomes clear that the Nazis are ready to attack us, we must do everything in our power to rise up against them." The prisoners decided to follow his advice. Some time later, after most of the prisoners had been transported from Warsaw, 500 remaining prisoners did stage a revolt. The Nazis killed every one of them.

As the Russian Army moved closer to Poland, the Germans decided to liquidate the special ghetto-clearing unit of which Halberstam was a member. All the prisoners were taken to a field outside of Warsaw, told to undress and stand near open pits, where soldiers prepared to machine-gun them. At the last moment, however, a car sped into the field. A high-ranking officer jumped out and communicated the special order from Berlin to stop the execution and send the prisoners to the Dachau concentration camp, where they were needed as slave laborers.

This unexpected reprieve, however, led to a brutal death march: for the next week, the prisoners were forced by SS soldiers wielding wooden clubs and steel bars to march 21 miles a day at top speed. In the blazing July heat, the emaciated prisoners were deprived of food and water and allowed to rest only at night. Those who couldn't keep up were shot.

On the third day, strained to the length of their endurance, the group was finally brought to rest for the night in a field surrounded by SS officers. As the guards slept, the Rebbe passed the word around: "Everyone should dig beneath himself. God's salvation comes in the blink of an eye." Each prisoner began to dig with his fingers, spoons, or pieces of wood. Remarkably, each found water, and small springs began to pop up everywhere, quenching everyone's thirst and giving them new life. Many years later, the Rebbe explained why he himself didn't drink from the water because the date was 9th Av, a traditional day of fasting to commemorate the destruction of the temple.[citation needed]

On the fifth day, the surviving marchers were packed into cattle cars for the rest of the journey to Dachau. Over the next few days, many succumbed to the overcrowding, lack of water, stench and heat in the cattle cars. Of the 6000 that set out on the death march, less than 2000 made it to Dachau alive. The Rebbe was one of the survivors.

From Dachau, the Rebbe was dispatched to the Muldorf Forest, where the Nazis were building an underground airport, hangar and missile batteries in order to bomb major European cities. He and thousands of other prisoners were forced to work 12-hour shifts, carrying 110-pound bags of cement from the rail depot to the cement mixers inside the hangar. Halberstam grew very weak from this difficult work. When he collapsed under his burden, he was beaten. He refused to work at all on Shabbat, which brought on more beatings. Finally, his friends persuaded the camp managers to give him to the job of camp custodian, allowing him to sweep and tidy the barracks while engaging in prayer the entire day.

Despite the hardships and privations, Halberstam was a beacon of strength and hope for his fellow prisoners. When one died in the infirmary—hardly a noteworthy occurrence in those days—the Rebbe stood up and eulogized him for having been a great Torah scholar in Hungary. He refused to eat non-kosher food or food cooked in the non-kosher kitchen, subsisting only on bread and water during his nine months in Muldorf. Moreover, he would not eat the bread until he had ritually washed his hands, and would often wait for days to find some water for this purpose. One prisoner watched him stand beside the cement mixer for hours at a time, collecting the drops of water that dripped from the tank.

As the war wound down in spring 1945, the Germans disbanded the Muldorf camp and sent the inmate population on yet another death march, chasing them from place to place without food or rest. Sometimes they were loaded aboard rail cars and driven to and fro. On Friday, April 27, the train suddenly stopped in a small town and SS officers jumped aboard, declaring, "You are free!" and ripping the Wehrmacht badges from their uniforms. Many prisoners believed them and jumped off the train. But Halberstam told the people around him, "Today is the eve of Shabbat. Where will we go?" Then he added, "My heart tells me that not everything here is as it should be." Suddenly, SS soldiers rode in on bicycles from all directions, firing machine guns and killing hundreds of people. At the same time, American bombers dove in, strafing the field. Only Halberstam and those who stayed with him on the train escaped injury. Two days later, their real liberation came when the train stopped near a village and the Nazi guards deserted them. American soldiers boarded the train with smiles, candy and chocolates.

The group was brought to the FeldafingDP camp near Munich, exhausted, demoralized and penniless. Here Halberstam's leadership qualities rose to the fore and he became the spokesman and leader of the religious survivors. He immediately arranged for the proper burial of those who had died by the train tracks, and demanded kosher food for the survivors. On the first Shabbat after liberation, he led the public prayer services in a newly opened synagogue and delivered a two-hour lecture, quoting from memory scholarly writings that he had last seen years before.

Halberstam's wife and ten of his children were murdered by the Nazis during World War II. His eldest son survived the war, but succumbed to illness in a nearby DP camp before his father even knew that he had survived. Yet Halberstam never complained of his lot, and avoided depression by reaching out to others. He spent much time listening to and comforting people of all ages, and brought hundreds of people back to religious observance through his passionate public speeches.

In fall 1945, Halberstam moved to the new DP camp of Föhrenwald, a larger location in Munich which he turned into the center of religious Jewish life for all the DP camps. Here the Rebbe created a communal survivors organization called She'aris Hapleitah ("the surviving remnant"), which operated religious schools for boys and girls and yeshivos for young men in 19 different DP camps. In addition, Halberstam set up a kosher slaughterhouse; built a kosher mikveh; acquired and distributed religious articles such as tzitzit, tefillin and mezuzot; raised money to help couples marry; and established Halakhic (Jewish legal) guidelines for men and women who had no proof of their spouse's death, enabling them to remarry and start new families.

On Yom Kippur, 1945, General Dwight D. Eisenhower visited the camps and came to see Halberstam, who had received a reputation as a "wonder rabbi". However, the Rebbe would not speak with him until he had finished his prayers. Afterwards he told the general, "I was praying before the General of Generals, King of Kings, the Holy One, Blessed be He. The earthly general had to wait." Impressed by the rabbi's leadership and frankness, Eisenhower asked him if there was any way he could help him in his efforts. In typical fashion, Halberstam asked for a small sample of the Four Species so that the survivors could properly celebrate the upcoming Sukkot holiday.

In spring 1946 the Rebbe made a special fund-raising trip to New York on behalf of She'eris HaPleita, raising $100,000, a huge sum in those days. That fall, he embarked on another fund-raising trip and decided to resettle in New York to strengthen the American Jewish community there and to continue working for Holocaust survivors from that side of the Atlantic. He established his court in the Williamsburg section of Brooklyn, New York, in 1947.[1]

On Friday, August 22, 1947,[3] he married his second wife, Chaya Nechama Ungar, the orphaned daughter of the Nitra Rav, Rabbi Shmuel Dovid Ungar. The match was made by Rabbi Michael Ber Weissmandl, Rabbi Ungar's son-in-law who had survived the Holocaust and re-established his yeshiva in Somerville, New Jersey.[1][3] The tenayim were held in Weissmandl's Nitra Yeshiva, while the chuppah and dancing were held at Yeshivas She'aris Hapleitah, the Rebbe's yeshiva in Somerville.[3]

Although the Klausenberger Rebbe had gone to great lengths to allow agunos and widowers to remarry after the Holocaust, relying on testimonies from people who had seen their spouses being led "to the left" in the Nazi selections rather than documented evidence, the Rebbe did not rely on the testimonies of his first wife's death. Instead, he sought the approval of 100 rabbis and sat on the ground for half an hour in mourning for his first wife before he remarried.[3]

He and his second wife had five daughters and two sons. His sons, Rabbi Tzvi Elimelech Halberstam and Rabbi Shmuel Dovid Halberstam, succeeded him, respectively, as Sanzer Rebbe of Netanya and Klausenberger-Sanz Rebbe of New York.

View of the dais at the cornerstone-laying ceremony for Laniado Hospital in 1974. Rabbi Yekusiel Yehudah Halberstam is seen at center left; his son, Rabbi Zvi Elimelech Halberstam (with glasses) is seated to his left.

The Rebbe's decision to move to the United States was not a permanent one. Throughout his travails in the Holocaust, he always had in mind the goal of settling in Israel. Toward that end, he established the Kiryat Sanz neighborhood in the beachside city of Netanya in 1958.[1] In so doing, he was the first Rebbe to establish a Haredi neighborhood in an Israeli development town. Over the next few years, he raised money for the establishment of key neighborhood institutions, including girls' and boys' schools and yeshivas, an orphanage, and an old-age home.[1]

The Rebbe moved permanently to Israel in 1960, settling in Netanya and directing both the community there and in Williamsburg. He also founded battei medrash and schools in other cities in Israel, and established the Kiryat Sanz neighborhood of Jerusalem as well.

In 1968 he founded another Sanz community in Union City, New Jersey,[4] and afterwards divided his time between that community and his residence in Netanya.[1]

The Rebbe is known for having established Laniado Hospital, a voluntary, not-for-profit 484-bed hospital in Kiryat Sanz, Netanya. The hospital is run according to Jewish law.

The vision for establishing the hospital originated during the Holocaust. At the cornerstone-laying for the second building in 1980, he told the assemblage in Yiddish:

I was saved from the gas chambers, saved from Hitler. I spent several years in Nazi death camps. Besides the fact that they murdered my wife and 11 children, my mother, my sisters and my brother – of my whole family, some 150 people, I was the only one who survived – I witnessed their cruelty. I remember as if it were today how they shot me in the arm. I was afraid to go to the Nazi infirmary, though there were doctors there. I knew that if I went in, I'd never come out alive. … Despite my fear of the Nazis, I plucked a leaf from a tree and stuck it to my wound to stanch the bleeding. Then I cut a branch and tied it around the wound to hold it in place. With God's help, it healed in three days. Then I promised myself that if, with God's help, I got well and got out of there, away from those resha'im (wicked people), I would build a hospital in Eretz Yisrael where every human being would be cared for with dignity. And the basis of that hospital would be that the doctors and nurses would believe that there is a God in this world and that when they treat a patient, they are fulfilling the greatest mitzvah in the Torah.[5]

In 1958, he laid the cornerstone for a community hospital to be run according to the strictest standards of Halakha. He petitioned the authorities for a building permit, but was not granted one until the left-wing Minister of Health left office in 1962 and the Health Ministry was given to a religious party. Halberstam spent 15 raising funds to build the hospital, which would come to be named Laniado Hospital, after the Laniado brothers, two bankers from Switzerland whose estate provided a $300,000 donation for the Rebbe.[5][6] The hospital's first building, an outpatient clinic, opened in 1975.[7] In the next few years, a maternity ward, emergency room, internal medicine department, a cardiology unit, and an intensive-care unit opened. The hospital continued to expand, and today encompasses two medical centers, a children’s hospital, a geriatric center and a nursing school, serving a regional population of over 450,000.[8] The Rebbe continued to plan and supervise the expansion of the hospital until his death in 1994.

In addition to his achievements in rebuilding the Sanz-Klausenberg dynasty and establishing many communal institutions, one of the Rebbe's most far-reaching accomplishments was his establishment of "Mifal HaShas" ("Talmud Factory") in 1982. This worldwide project encourages thousands of Jewish men and boys to study copious amounts of Talmud and Shulchan Aruch and complete written tests on 20–30 pages per month in return for a monthly stipend. Mifal HaShas continues to operate today worldwide. The Israeli and European operations are under the leadership of Zvi Elimelech Halberstam, the Rebbe's oldest son and current Sanz-Klausenberger Rebbe of Israel. The North American operations are under the leadership of Samuel David Halberstam, the Rebbe's son and current Sanz-Klausenberger Rebbe of Brooklyn.

The Rebbe recorded his Torah novellae in Shefa Chayim and She'eilos Uteshuvos Divrei Yatziv.

Halberstam died on June 18, 1994, and was buried in Netanya. In his will, he divided leadership of the Sanzer Hasidim between his two sons, His elder son, Zvi Elimelech Halberstam, became the Sanz-Klausenberger Rebbe (also known as the Sanzer Rebbe) of Netanya, and Samuel David Halberstam became the Sanz-Klausenberger Rebbe of Brooklyn.